1. Field of the Invention
The invention relates to a cast stone for securing outdoor traffic areas.
2. Description of the Prior Art
The invention relates to a cast stone made particularly from concrete, for securing traffic areas outdoors, with the stone having at least one pair formed by a protrusion and an adjacent recess substantially matching the form of the protrusion of the adjoining laid stone on its lateral faces extending vertical to the plane of laying and in substantially mutually parallel relationship and with the sequence of protrusion and recess having the same form on all lateral faces in the circumferential direction of the cast stone.
Such cast stones, which are to include plates, particularly plates of concrete, can be optionally provided with a textured surface over their entire area. Since the sequence of protrusion and recess is the same in the circumferential direction of all cast stones, no special attention is required for the laying work. In the way in which they get into the hands of the worker, the cast stones can be set against previously laid stones. The mutual interlocking of the stones obtained with the aforementioned means furthermore results in a bonding which is effective in both directions parallel to the associated lateral faces, whereby there is obtained a cover which in regard to strength parallel to the plane of laying sustains all usually developing load conditions.
In regard to the joint of adjacent stones there exists the regulation that such a joint must have a minimum width of about 2 to 5 millimetres to conform to the respective national regulation so that thermal expansions are absorbed and production tolerances of the cover made from the stones are accommodated and that the filler material of the joints, usually sand, commonly washed in after laying the stones, fills the joints without cavities remaining. When the stones are laid by hand, such a form of joints can be provided by the operator by ensuring that the spacing of adjoining stones or the development of the joint according to regulations are obtained, for instance by extending strings along which the stones are aligned during the laying work.
But the related work is time consuming and requires the employment of trained persons. When the stones are to be laid by a machine making use of appropriate mechanical means—for which purpose the stones are combined into a larger number of structure units containing stones in mutually bonded relationship—the development of the joints according to regulations is not possible. As a matter of fact, when such structure units are set down for laying, the stones get spaced, in the average, by about one millimetre. The resulting joint does not correspond to the nominal width of 3 to 5 millimetres specified by the standards.
In order to overcome the above-described problems, it has been known for cast stones with flat lateral faces, to provide these lateral faces with an increased number of cog-like protrusions, with the protrusions having in the direction perpendicular to the associated lateral face a height such that in an unguided setdown, the required width of the joint is obtained, and this even when the stones are set down by machines in the above-described form of so-called structure units. These protrusions, which are usually required in larger numbers, necessitate an accordingly expensive form of the moulds for producing the cast stones and, in corresponding numbers, they still form spots at which the filler material for the joints is prevented from penetrating into the joints so that cavities into which the filler later sags, cannot be avoided.
It is therefore the problem underlying the invention to indicate for cast stones of the above-specified type a possibility of ensuring the prescribed joint spacing with a minimum number of these spacer elements, wherein particularly crucial measures to be satisfied by the tools used for moulding the stones are avoided.